What version of ACF are you using?
// ACF >= 5.5.0
$queried_object = get_queried_object(); // gets the term
$post_id = 'term_'.$queried_object->term_id;
$image = get_field('image_field_name', $post_id);
// ACF < 5.5.0 - will also work on >= 5.5.0
$queried_object = get_queried_object(); // gets the term
$post_id = $queried_object->taxonomy.'_'.$queried_object->term_id;
$image = get_field('image_field_name', $post_id);
for more information see the section on getting field values from different objects on this page https://www.advancedcustomfields.com/resources/get_field/
